Chemical treatment of petroleum distillates



March 25, "1941. L, u. FRANKLIN 2,235.921

CHEMICAL TREATMENT OF PETROLEUM DISTILLATES Filed Feb. 24, 1957 70 TREATED MATE IAL Z] Wu c whim Patented Mar. 25, 1941 UNITED STATES PATENT OFFICE CHEMICAL TREATMENT OF PETROLEUM DISTILLATES ration of Pennsylvania Application February 24,

1 Claim.

This invention relates to chemical treatment of petroleum distillates, especially to the sweetening of light distillates such as gasoline and kerosene, and more particularly this invention comprises a process wherein there is first created a mass of discrete particles or substantially non-adsorbent. and non-absorbent material, which particles are interspersed with or coated with either cupric chloride or a mixture of cuprio sulfate and sodium 10 chloride; wherein the light distillate to be treated ls percolated through the said mass of discrete aarticles, reacting with the copper compounds; and wherein the said copper compounds are regenerated by means of periodic or continuous supply of oxygen thereto.

Substantially all light distillate-s of petroleum contain some sulfur compounds. The constitution and behavior of the particular compounds varies greatly among samples from various sources and these will vary in material from any specific source according to the particularcondi-tions to; which it has been subjected. Sulfur which is present in the form of mercaptans is the most objectionable form, Fractionation, filtration, and treatment of the distillate with sulfuric acid, S02, aluminum chloride, etc., are the only feasible methods for substantially reducing the sulfur content of the distillate, but each of these has its practical limitations and none is capable of removing all the mercaptans. Beyond the point attained by these means the sulfur compounds are most effectively dealt with by conversion to the least objectionable form, and the generally accepted mode of doing this is to sublest the distillate to a treatment which will convert the mercaptans to disulfldes. For many years this has been done with sodium plumbite by the well known doctor treatment. This con.-

version of the mercaptan content of a distillate to a disulfide is commonly known as sweetening and a distillate containing mercaptans is termed sour and a distillate in which the sulfur has been converted to disulfides is termed sweet. The object of this invention is to provide a process by which it is possible to sweeten a sour distillate while avoiding most of the shortcomings of the doctor treatment and to attain additional advantages as will be more particularly set forth in the following discussion.

The well known doctor treatment has a number of inherent disadvantages, the most important of which are the high cost for caustic soda, for litharge, and for sulfur; the amount of doctor treatment to be used for difierent lots of material has had to be determined experimentally;

1937, Serial No. 127,515

the treatment consumes a substantial period of time and it is often necessary to wait some hours for the lead sulfide to break out and settle from the material being treated; the process produces a considerable amount of lead sulfide which must be removed and disposed of; and the process entails a treating loss of from /2% to 1% of the material undergoing treatment.

On the other hand, the process of this inven tion produces a clear bright product of color at least equal to the untreated material; it produces a finished product which is characterized by a previously unattainable stability of color when exposed to sunlight; the treated material ordinarily causes less corrosion when subjected to the well known copper strip test; due to the absence of alkali or elementary sulfur, this process retains in the distillate naturally formed gum inhibitors which have long been destroyed by doctor treatment; and the material undergoing treatment leaves the process with as high antiknock value as the untreated material.

The figure of the drawing illustrates schematically an apparatus useful in the conduct of the process of my invention.

Referring to the drawing l represents a vertically positioned cylindrical tank, with removable cover 3 and base 4. A short distance above the bottom of tank I is a foraminous plate 5. A manhole 6, for cleaning purposes, is positioned in the side of tank I, slightly above and close to the foraminous plate 5. Entering the side of tank I, at points below foraminous plate 5, are lines 1, 8, and 9 for introducing untreated gasoline, v air, and steam, respectively, into the tank. Close to the top of tank I is a water inlet line IEI, which terminates in a sprayhead H. Also close to the top of the tank I is a line l2 for conducting treated material from the tank.

This drawing is of a system in which the gasoline flows upward through the catalyst bed. It is in many cases equally desirable, and in some cases preferable, to have the flow in the opposite direction. When it is intended to operate with downward flow it is necessary to have air and steam connections into the top of chamber l and this can ordinarily be done most handily by making separate air, steam, and water connections to line In and introducing all of these, as needed, through sprayhead II. Greatest fiexibili-ty of operation is had when air and steam and distillate inlet and outlet connections are made below foraminous plate 5 and also at the top of chamber l, above the point to which it is intended to fill with catalyst. 5t

In the conduct of my invention I first fill the tank I with a mass of catalytic material 2, using the foraminous plate 5 in the bottom of tank I as a supporting means for the catalyst, and I fill the tank with catalyst to a point below sprayhead II and exit line I2. The tank is so proportioned that it will hold a bed of catalyst anywhere from about two feet to twenty feet deep. The actual depth of the catalyst bed depends principally on the rate at which it is desired to sweeten material through it, but in practice I prefer a depth not much les than three feet and from that depth on up, depending upon the fineness or coarseness of the discrete particles which carry the catalyst, and upon the desired rate of operation and upon the ease or difficulty with which a particular light distillate is sweetened. A depth of twenty feet is ofttimes found to be not too much.

My catalyst is cupric chloride, and I may charge it into my treating chamber as such or I may charge a mixture of cupric sulfate and sodium chloride and so form the cupric chloride in place, as needed. I use these materials in the form of a moist surface coating on tiny particles of a non-adsorbent and non-absorbent material such as ordinary silica sand. In the conduct of my invention the sour distillate which is to be treated is passed through a bed of the before-described catalyst and in its passage therethrough the mercaptans are converted to disulfides. When cupric chloride is the specific material charged to the catalyst bed the reactions are as follows:

Disulfide Hydrochloric Mcrcaptau Gupric h acid Cuprous c loride Ouprous Cupric Cuprous mercaptide chloride chloride After all of the mercaptans have been so converted to disulfides it is possible to reconvert the cuprous chloride to cupric chloride and so make the process a continuous self-generating one. This is done by introducing air into the catalyst bed through line 8, The reaction by which this revivification is accomplished is as follows:

4CuCl 41161 0: 401101: 21110 Ouprous Hydrochloric Oxygen Oupric Water chloride acid chloride From the foregoing formulae there can be derived an overall statement of the process in the following form:

NazSOH-CuClg Sodium Cupric sulfate chloride CuS04+2NaCl Cupric Sodium sulfate chloride I find that the use of cupric chloride alone in the catalyst bed will sweeten the distillate more quickly than when I have cupric sulfate and sodium chloride there, but the straight cupric chloride has a distinct tendency to throw the distillate off color. This I find to be largely due to the presence of an excess of cupric chloride,

Ordinary silica sand is especially desirable as the non-adsorbent and non-absorbent material which is to be coated with my catalyst. This is so because it provides the desired tiny interstices which will set up capillary attraction and give excellent contact between the catalyst and the material undergoing treatment, but which interstices will be accessible to the oxygen which is used to regenerate the catalyst. In this connection I wish particularly to emphasize the importance of notusing an absorbent material saturated with the catalyst. In such a case the catalyst is accessible to the distillate undergoing treatment but that catalyst, after such use, is not accessible to the gas which is used for regeneration of the catalyst. The result is that the continued contact of the flowing distillate with the unregenerated catalyst results in the distillate taking up copper and being discolored thereby.

While sand has served very satisfactorily as the carrier of my catalyst for operations on the scaleon which I have conducted a large portion of my operations, I nevertheless find tiny glass beads and various crystals very satisfactory, particularly for extremely large scale operations. When crystals are used they must of course be of a material which is not soluble in and which does not react with the material undergoing treatment or the catalyst. In the use of sand I find well screened and uniformly sized particles advantageous.

I have-previously stated that I use my catalyst in the form ,of a moist surface coating on the non-absorbent particles which have just been described and I desire to further emphasize the necessity of the catalyst being moist. This is indispensable in my process. This moisture acts as an ionization medium, thus permitting reactivation of the catalyst with oxygen; it afiixes the particles of catalyst to the particles of carrier, thereby preventing their migration through and out of the catalyst chamber; and it acts as a precipitating agent to precipitate the chemically combined copper compounds out of the sweetened distillate, this being especially important when sweetening cracked distillate.

Some types of distillate sweeten better when the catalyst bed is kept much more moist than is necessary with other distillates. Also, if the distillate is charged in a dry condition to the sweetening chamber I there will be a tendency of the distillate to carry 011 some of the moisture and it then becomes necessary to introduce additional water into the catalyst bed. The moistening of the catalyst must be done with care because of the solubilities of cupric chloride, cupric sulfate, and sodium chloride in water. I desire to have the catalyst bed moist but not pasty. The most satisfactory way of getting moisture into the bed originally is to moisten the materials in originally preparing the bed, before their introduction into chamber I. After that, for restoring moisture which is taken up and carried out by the dry distillate passing through, I introduce a jet of steam through line 9 into the distillate in the bottom of chamber I, below foraminous plate 5, and I find that moisture introduced in this way is so finely dispersed in the distillate that it will carry up through the catalyst bed for a considerable distance. If the catalyst bed is an extremely deep one it may be necessary, in

order to add moisture to the upper part of the bed, to reverse the fiow and pump distillate into the bed through the customary exit line 12, simultaneously introducing steam into the distillate through line Ill and sprayhead H.

A most important distinction between my process and other processes of sweetening light distillates with copper compounds is that the distillate leaving the catalyst chamber of my process is altogether sweet, not discolored by the presence of chemically combined copper compounds, and that the material therefore does not require a wash or require subsequent chemical treatment such as the common after-treat with sodium sulfide, zinc sulfide, or other sulfides, either dry or in solution.

Through the foregoing portions of this specification I have frequently referred to the use of cupric sulfate and sodium chloride to form cupric chloride in place, as needed. While these materials are inexpensive and convenient and have proven highly effective for the purpose, I have also used other chlorides and other copper compounds and I find that all water soluble chlorides and all water soluble copper compounds, reacting with one another to form cupric chloride, are effective in my process. Specific examples of other pairs of these are calcium chloride and cupric nitrate, ferric chloride and cupric sulfate, and ammonium chloride and cuprlc nitrate. Further, for the purpose of my specification and claim, I use the words Water soluble to comprehend compounds which have at least enough solubility in water to permit ionization; and when I speak of a moist reagent or catalyst I mean one containing at least enough water to permit ionization.

In the claim appended hereto, when I speak of light petroleum distillates I especially mean the non-viscous low boiling products of petroleum such as gasoline, naphtha and kerosene; and I use the language to comprehend all light hydrocarbons of comparable nature, whether or not they be distillates, specifically including light products from polymerization of gas and from other newer methods of rearrangement and synthesis of hydrocarbons.

In the claim appended hereto, when I speak of conducting my process in the absence of ab sorbent or adsorbent materials I mean thereby any such material other than the chlorides and copper compounds used to effect the sweetening, and the products of the sweetening reaction.

In the claim appended hereto, when I speak of contacting the copper compound with oxygen I use that language to comprehend any such contacting, whether it be continuous or intermittent; whether the contacting be with relatively pure oxygen or air or other mixture of oxygen with some gas which would be inert in the system; and whether or not the contacting be accomplished inside of treating tank I or outside of said tank.

What I claim is:

The process of sweetening a sour petroleum distillate, which comprises passing such a distillate through a pervious bed of small non-absorbent, non-porous inert solid particles moistened with an aqueous medium containing cllpric and chloride ions, capable of reaction with mercaptans present in the distillate to form disuliides and cuprous chloride capable of regeneration by means of oxygen, and supplying sufficient moisture to the bed in addition to any formed in regeneration, to supplant moisture removed in excess by entrainment in said distillate and to maintain the bed in a substantially uniformly moist but not pasty condition.

LESLIE U. FRANKLIN, 

